Orthotic pads are generally materials that are used in apposition to a mammalian body part in order to support and/or cushion that body part. Such pads can be used alone, i.e., as orthotic articles themselves, or in conjunction with other orthotic devices, e.g., harnesses, braces, straps and the like. Generally either the pad, the device, or both are custom-fitted in order to directly address and resolve the user's orthopedic needs.
Such pads can be used in a variety of ways including, e.g., as cushioning, such as for sports equipment or for therapeutic orthotic devices; as a support for weight-bearing applications, such as within an artificial leg; as padding within an immobilizing device, such as a cast; for protection from physical impact with another object, and so on.
The types of materials typically used for such purposes are as widely diverse as the uses themselves. For instance, materials such as trapped air, air bladders, foam rubber, styrofoam and felt are frequently used, depending on the application. See, for example, U.S. Pat. Nos. 4,280,489, 4,347,213, 4,370,976 and 4,565,250. Such materials generally have either sufficient strength for weight-bearing applications or sufficient resilience for comfort, but not both. Nor do the materials generally permanently conform with much accuracy to the shape of the body unless specially prepared, e.g., cut, molded or sculpted in an indirect manner.
Other types of materials, such as two-part foams and injectable foams can often be conformed to the shape of the body, are frequently somewhat stronger, and have been used for such purposes as ski boot inserts. See, e.g., U.S. Pat. Nos., 4,083,127, 4,144,658, 4,182,056, 4,245,410, 4,255,202, 4,301,564, and 4,414,762. Their use however is generally restricted to applications in which an outer shell, e.g., a portion of the ski boot itself, is available to contain the foam after it is mixed or injected and as it sets and cures. Moreover, the resultant cured foam would generally exhibit uniform density throughout its structure, and, in turn, uniform weight-bearing strength and cushioning properties, regardless of the potentially differing needs of different portions of the opposing body part.
A particularly important area for the use of orthotic pads is in the field of footwear, i.e., as orthotic footpads. Such orthotic footpads are typically prepared and fitted by an orthopedist or podiatrist and used to correct or compensate for certain orthopedic problems and abnormalities, e.g., in the foot itself, or perhaps even in the gait or posture of the patient.
Orthotic footpads can be used as inserts within other footwear, e.g., inside shoes or boots, or can be used alone, e.g., as the soles of shoes, or as custom-made sandals or portions of sandals. Materials described as useful for orthotic footpads and other devices include those described, e.g., in U.S. Pat. Nos., 4,211,019, 4,232,457, 4,325,380, 4,346,525, 4,439,934, 4,470,782, 4,520,581, 4,522,777, 4,597,196 and 4,628,621.
In selecting suitable materials for the preparation of orthotic pads, several criteria must be considered. Firstly, the materials should be of a type that can be quickly, easily, safely and permanently formed to the desired shape and position. Further, the finished orthotic pad should be sufficiently strong for its intended (e.g., supportive) purpose, yet should be sufficiently soft and resilient to be comfortable in use, e.g., while supporting weight, cushioning, and so on. Lastly, the finished orthotic pad should be durable enough to withstand the rigors of repeated and demanding use. Materials heretofore described in the art as useful for preparing orthotic pads can meet only some of these qualities but not all.
From the foregoing, it will be appreciated that improved materials and methods are needed for preparing orthotic pads that are readily conformable, and have proper weight-bearing strength as well as cushioning properties.